U.S. patent application number 09/893215 was filed with the patent office on 2002-12-26 for tensile load sensing belt.
Invention is credited to Clarke, Arthur, Metzen, Hans-Dieter.
Application Number | 20020194935 09/893215 |
Document ID | / |
Family ID | 25401214 |
Filed Date | 2002-12-26 |
United States Patent
Application |
20020194935 |
Kind Code |
A1 |
Clarke, Arthur ; et
al. |
December 26, 2002 |
Tensile load sensing belt
Abstract
The invention comprises a lifting belt having at least one
tensile member adapted to function as a sensor and a load bearing
member. The belt comprises an insulating elastomeric body in which
the tensile member is enclosed. The tensile member comprises a
series electrical circuit connected to a bridge circuit for
detecting resistance changes in the tensile member caused by a
strain in the tensile member.
Inventors: |
Clarke, Arthur; (Dumfries
and Galloway, GB) ; Metzen, Hans-Dieter; (Juelich,
DE) |
Correspondence
Address: |
Jeffrey Thurnau
The Gates Corporation
Mail Stop 31-4-1-A3
900 S. Broadway
Denver
CO
80209
US
|
Family ID: |
25401214 |
Appl. No.: |
09/893215 |
Filed: |
June 26, 2001 |
Current U.S.
Class: |
73/862.391 |
Current CPC
Class: |
B66B 7/1223 20130101;
D07B 1/145 20130101; G01L 5/102 20130101 |
Class at
Publication: |
73/862.391 |
International
Class: |
G01L 001/26 |
Claims
We claim:
1. A lifting belt comprising: an elastomeric body; at least one
conducting tensile member having a resistance and extending within
the body; and the conducting tensile member having a first lead and
second lead for making a connection to an electrical circuit.
2. The belt as in claim 1, wherein the belt is endless and the belt
further comprises sides extending along a length of the belt.
3. The belt as in claim 1, wherein the belt comprises a length
having opposing ends.
4. The belt as in claim 1 further comprising: an electrical
circuit, the electrical circuit comprising a voltage bridge for
measuring a conducting tensile member resistance change.
5. The belt as in claim 3 further comprising: a plurality of
parallel conducting tensile members extending through the body
along a major axis, each conducting tensile member electrically
connected in series to an adjacent conducting tensile member
whereby a series circuit is formed.
6. The belt as in claim 5, wherein the elastomeric body is an
electrical insulator to prevent an electrical contact between
adjacent conducting tensile members.
7. The belt as in claim 2, wherein the first lead and the second
lead each extend on a belt side for contacting a conductor.
8. The belt as in claim 6, wherein the elastomeric body has a
dielectric constant in the range of 1.5-10.0.
9. A lifting belt system comprising: an elastomeric body having
opposing ends; at least one tensile member extending within the
body along an axis and having a resistance; the tensile member
having a lead at each end connected to an electrical circuit; and
the electrical circuit for measuring a voltage change across the
tensile member.
10. The system as in claim 9 wherein the electrical circuit further
comprises: a voltage bridge whereby a strain change in the tensile
member is detected.
11. The system as in claim 9, wherein the elastomeric body is an
electrical insulator to prevent an electrical contact between
adjacent tensile members.
12. The system as in claim 9, wherein the elastomeric body has a
dielectric constant in the range of 1.5-10.0.
13. The system as in claim 9 further comprising a protrusion on at
least one end of the belt for engagement with a mounting
device.
14. The system as in claim 5 further comprising a protrusion on at
least one end of the belt for connection to a mounting device.
Description
FIELD OF THE INVENTION
[0001] The invention relates to load bearing lifting belts, in
particular, to a tensile load sensing lifting belt for connecting
to a circuit for detecting a strain change in a tensile member.
BACKGROUND OF THE INVENTION
[0002] Lifting belts generally comprise a tensile member contained
within an elastomeric outer covering. The belt tensile member is
for the most part used solely to provide the means of supporting
the weight to be lifted.
[0003] Prior art wire ropes are available that combine a sensor and
load bearing capability. These use the wire rope tensile members as
strained elements in combination with a voltage bridge for
measuring a strain in the tensile member. However, these wire ropes
are not continuous and comprise a plurality of parallel conductors
that are connected to attachment ends of the rope. They also
comprise connectors at each end whereby the rope is connected to a
load.
[0004] Representative of the art is U.S. Pat. No. 3,958,455 (1976)
to Russell which discloses a transducer of the resistance wire rope
type wherein strained resistance wires are adapted to function both
as a sensor and load bearing member.
[0005] Also representative of the art is U.S. Pat. No. 3,950,984
(1976) to Russell which discloses a transducer of the resistance
wire rope type wherein strained resistance wires are adapted to
function both as a sensor and load bearing member.
[0006] What is needed is a lifting belt having a tensile member
having a resistance used as a sensor and load bearing member
enclosed in a dielectric elastomeric body. The present invention
meets this need.
SUMMARY OF THE INVENTION
[0007] The primary aspect of the invention is to provide a lifting
belt having a tensile member having a resistance used as a sensor
and load bearing member enclosed in a dielectric elastomeric
body.
[0008] Other aspects of the invention will be pointed out or made
obvious by the following description of the invention and the
accompanying drawings.
[0009] The invention comprises a lifting belt having at least one
tensile member adapted to function as a sensor and a load bearing
member. The tensile member has a predetermined resistance. The belt
comprises an electrically insulating elastomeric body in which the
tensile member is enclosed. The tensile member comprises a portion
of a series electrical circuit connected to a bridge circuit for
detecting resistance changes in the tensile member caused by a
strain in the tensile member.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] FIG. 1 is a schematic view of the inventive system.
[0011] FIG. 2 is a cross-sectional view of the belt.
[0012] FIG. 3 is a cross-sectional view at line 3-3 in FIG. 1.
[0013] FIG. 4 is a graph of the resistance of a tensile member
versus belt tension.
[0014] FIG. 5 is a sectional perspective view of an alternate
embodiment.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0015] FIG. 1 is a schematic view of the inventive system. Belt 100
comprises tensile cords running the full length of the belt along a
major axis. Tensile cords 10 are embedded in elastomeric material
11 in such a way so as to prevent contact between adjacent cords 10
along the length of the belt.
[0016] Each tensile cord is connected in series to the next cord at
alternate ends of the belt to form a series circuit. Leads 201 and
202 extend from an end of belt 100 for connecting to a Wheatstone
bridge 200 or other four arm or two arm voltage/resistance bridge.
A meter or other appropriate output display 300 can be connected
across the bridge to provide a visual reading of a voltage across
the bridge and thereby across the tensile member.
[0017] Tensile cords 10 comprise metallic wires or cords that bear
and support a load. Cords 10 are electrically conductive.
[0018] Alternatively, a single conductive tensile cord 10 may
extend along the length of the belt to which leads 200 and 201 are
connected at each end in the manner described herein. The single
conductive tensile cord would be used in conjunction with other
conductive or non-conductive tensile cords, depending on the load
bearing requirements of the belt.
[0019] Elastomeric 11 may comprise any one of a number of known
elastomer compositions known in the art including but not limited
to chloroprene rubber or EPDM. Elastomeric 11 is dielectric in
order to electrically insulate each tensile cord from the others
along the length of the belt body. A dielectric constant,
.epsilon..sub.r, for the elastomeric is in the range of 1.5 to
10.0.
[0020] Resistors R2, R3, and R4 have known resistance values and R1
is a resistance of the tensile cord series circuit. A change in the
tension/strain or a break in the tensile cord circuit will affect
R1, thereby changing a voltage V across the bridge. The change
would register on display 300.
[0021] The magnitude of R1 is first measured in the unstressed or
unloaded condition. R4 is then adjusted to balance the bridge in
the unstressed condition. Then, as the belt is loaded, the strain
changes the resistivity of the tensile cords, causing a voltage V
to change. The voltage change may include registration of strain up
to and including total failure of one or all of the tensile cords.
One can appreciate that failure of a single tensile cord on the
circuit will cause resistance R1 to approach .infin. .omega.. This
will result in a marked change in voltage V across the bridge,
alerting a user who can then take the equipment out of service or
make repairs.
[0022] In service, belt 100 is clamped at each end by mounting
bracket M1 and M2. Each mounting bracket grips the belt body,
thereby affixing it to a cable drum or elevator car or other piece
of equipment. In the preferred embodiment the belt has discrete
ends to which the mounting brackets are clamped, such as in the
case of a rope, as opposed to an endless belt.
[0023] In an alternate embodiment the belt comprises an endless or
continuous member, also operating in a lifting capacity. In the
alternate embodiment leads 201 and 202 project from a side of the
belt body, or the leads extend along a side of the continuous belt
as shown in FIG. 5. The tensile cords 10 are connected in series as
described herein with the side leads 500, 501 located on the sides
of the belt, 507, 508 respectively, for connecting the belt to the
bridge circuit. Leads 500, 501 contact a conductor for receiving a
voltage signal, such as conductive pulley flanges (not shown)
during operation. The leads 500, 501 would be operationally similar
to electric motor brushes in this way, electrically connecting to
the pulley flanges during each pass through a pulley. Leads 500,
501 may also extend or project along sides 505 and 506. The belt
leads would again comprise any electrically conductive material
suited for the use, such as steel or carbon materials. This
alternate embodiment may be used to indicate changes in belt
tension caused by load changes or by normal wear, allowing
adjustment thereof by use of a tensioning idler.
[0024] The preferred belt has an overall length sufficient for
service in an elevator system or for use on forklifts. The strain
gage aspect of the belt would alert a user to an overload condition
through high strain or to potential degradation of condition of the
tensile member, for example, failure of strands within a stranded
tensile member.
[0025] FIG. 2 is a cross-sectional view of the belt. Belt 100 has
an overall width w and an overall height h. The aspect ratio w/h of
the preferred embodiment is generally in the range of 1 to 30, but
may comprise any suited to the particular application. Tensile
cords 10 are substantially parallel to each other along a length of
the belt.
[0026] Jumpers 12 are shown between adjacent tensile members 10.
Jumpers 12 comprise conductors and are a portion of the series
circuit between the tensile members. The jumpers are embedded
within the belt body 11 and are located at each end of the belt. A
like set of jumpers (not shown) is present on the opposing end of
the belt, also comprising a portion of the series circuit, see FIG.
1.
[0027] FIG. 3 is a cross-sectional view at line 3-3 in FIG. 1.
Clamp M2 engages an end of the belt 100 adjacent to protrusions 13,
14. In the preferred embodiment, protrusions 13, 14 extend across a
width w of the belt. A single protrusion may also be used, for
example, protrusion 13. Protrusions 13, 14 provide a positive
mechanical engagement for the clamp to the belt to prevent the belt
from being pulled through the clamp when it is under load L.
Protrusions may also be used at the other end of the belt (not
shown) in a like manner as shown in FIG. 3.
[0028] FIG. 4 is a graph of the resistance of a tensile member
versus belt tension. The example depicted in the graph comprises a
belt having ten steel cords 10 that are serially connected. The
y-axis depicts the increase in resistance over a given base value
for R1. The base value for R1 is measured in the unstressed
condition. One can see that the resistance increases generally
linearly with the increase in tension or load. One can appreciate
that the resistance would continue to increase with load until one
or all of the tensile cords fails. Upon failure of a tensile cord
the resistance goes to .infin. .omega..
[0029] Compilation of the resistance readings over time would be a
helpful tool in identifying belt maintenance intervals or to
predict failures.
[0030] Although a form of the invention has been described herein,
it will be obvious to those skilled in the art that variations may
be made in the construction and relation of parts without departing
from the spirit and scope of the invention described herein.
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